Radiation isomerization process



c. E. HEATH ETAL RADIATION ISOMERIZATION PROCESS Filed April 29,1957

NORMAL PARAFFINIC. 3 5 HYDROCARBON FEED 5 AICI 4 ISOPARAFFINS RADIATION9 6 SOURCE 1 PRODUCT 6 SEPARATION f 4- 17 f METHYL CYCLOPENTANE Carl E.Heath mentors Peter J. Lucchesi Attorney 2,956,941 RADIATIONISOMERIIZATION rnocnss Carl E. Heath, Nixon, and Peter J. Lucchesi,Cranford,

N.J., assignors to Esso Research and Engineering Company, a corporationof Delaware Filed Apr. 29, 1957, Ser. ism 655,907 Claims. cifzo t-iszThis invention relates to the isomerization ofparafiinic 2,956,941Patented Oct 18,1960

a y, methyl cyclopentane is employed in the present'method as a crackingsuppressor when'added to paraflins in concentrations-ol 2 to 20 wt.percent. Ad-

hydrocarbons. -More particularly, it relates to an im--.' proved methodfor producing saturated branched-chain hydrocarbons by the reaction ofparafiinic hydrocarbons with an aluminum chloride catalyst in thepresence of high energy ionizing radiation. The products are normallyliquid saturated branched-chain hydrocarbons boiling chiefly within themotor fuel boiling range, i.e. 85 F. to 440 F.

In brief compass,- this invention proposes a radioisomerization processin which hydrocarbon cracking and secondary alkylation reactions aresubstantially eliminated. According to the present discovery, suchbeneficial results are surprisingly achieved when straight-chainparafiins are contacted under isomerization reaction conditions withaluminum chloride in the presence of promotional amounts of a naphthene,the reaction being carried out in the presence of high energy ionizingradiation.

Straight-chain parafiins of at least 4 carbon atoms per moleculeheretofore have been isomerized in the' presence of Friedel-Crafts typecatalysts to produce branched-chain parafiins. Greatly increased yieldsof isomerized hydrocarbons have now been obtained by isomerizing inthepresence of an aluminum chloride catalyst and exposing the catalyst tohigh energy ionizing radiation during the isomerization. In such aprocess, however, secondary reactions occur which lower the u lti mateyield of isomerized product. These reactions are I hydrocarbon crackingand secondary alkyla'tion pro'e'sses between the fragments. 1

8 carbon atomsare isomerized in the presence of aluminum chioricie in anamount of from about 2 to 200 wt.

percehtb'ased upon the weight of parafiin, by adding to the feed fromabout 2 to wt. percent based upon the weight of .paraflin, of acycloparaffin having between 5 and 8 carbon atoms and exposing thealuminum chloride to high energy ionizing radiation until at least about1 10 kwh. of radiation energy per pound of paratfin has been absorbed;Preferably paraffin conversion is carried out at a temperature in therange of about 40 to 300" F;

Suitablenaphthenes for the purposes of the present invention arecycloparatfins boiling in the range of from about 40 to 110 C. Forexample, methyl cyclopentane,

vantageously from about 5 to about 10% of methyl cyclopentane, based onthe weight of hydrocarbons, is added as a cracking suppressor to aradioisomerization process according to this invention.

In one embdoiment of the invention, pure straightchain parafiinhydrocarbons are employed as the feed stock for the novel conversionprocess. Normal butane, normal pentane, normal hexane, normal heptaneand the like, as pure compounds, can be subjected to the isomerizationtreatment as hereinafter more fully described. The

processof the present invention equally as well applies to the treatmentof mixtures of hydrocarbons predominantly composed of straight-chainparafiinic constituents. The invention is not limited to theisomerization of straighti chain hydrocarbons but encompasses also theconversion of branched-chain hydrocarbons to isomeric more highlybranched-chain hydrocarbons. Mixed paraflins such as straight-runnaphthas also can be converted by the present method into isomericmixtures which have increased value with respect to anti-detonationqualities when used as motor fuels. In general, any hydrocarbon mixturecomprising at least 75 wt. percent parafiinic hydrocarbons is suitablefor use as a feed stock for the process herein outlined. Particularlyadvantageous for this process is a feed stock containing at least 75 Wt.percent based on the totalweight of hydrocarbon present of paraflinshaving from 4 to 8 carbon atoms and boiling in the range of from aboutto 200 F. A product containing substantial amounts of branched-chainisomers can be separated from the reaction medium and fractionatedwithin the'desired boiling range. The unconverted hydrocarbons can thenbe returned to the isomerizing reactor, to be further isomerized in anormal recycle process.

cyclohexane,"methy1 cyclohexane, ethyl cyclopentane, 11,1-

e isomerization reaction of the present invention is carried out byexposing the reactants and the isomerization catalyst to high energyionizing radiation, that is, high energy quanta (radiation wave lengthless than 50 A.), neutrons, and charged and uncharged particles ofatomic and sub-atomic nature having energies greater than about 30electron volts. Types of radiation suitable for the purposes ofinvention include high energy electromagnetic radiation such as gammarays and X-rays and high velocity electrons, as well as beta rays andalpha particles. These types of radiation can be supplied bynaturally-occurring radioactive materials which emit alpha, beta andgamma rays.

Fission by-products of processes generating atomic power, or fissionablematerials which emit high energy gamma rays also afford a highlydesirable and most abundant source of radioactivity suitable for thepurposes of the invention. These by-products include those with atomicnumbers ranging from 30 to 63 and their compounds. They are formed inthe course of converting uranium and thorium and other fissionablematerials in an atomic reactor. By high energy ionizing radiation ismeant radiation from terrestrial sources of sufiicient intensity suchthat the dose rate is at least l l0 kwh./ hr./ lb. of reactant. Thisexcludes radiation such as cosmic and ultraviolet which are ineffectualfor the purposes of this invention.

Materials made radioactive by exposure to neutron irradiation, such asradioactive cobalt-60, which emits gamma rays, can likewise be used.Suitable sources of high velocity electrons are thebeams of electronaccelerators, such as the Van de Graafi electrostatic accelerator. Ingeneral, however, high velocity electrons and high energy gammaradiation and its well-known sources such as nuclearfission by-productsand materials made radioactive by neutron irradiation, are preferred forthe purposes of the invention mainly because of the relatively highpenetrating power of the rays and the availability and ease ofapplication .of these sources of radiation.

For isomerization reactions in accordance with the present invention, awide radiation dose range can be employed, for example, from about 10-to about 10 megaroentgens. This is approximately equal to a dosage offrom 10- to 10 kWh/lb. of paratfin. Preferably the radiation doseutilized is between about 10- and 10 kWh/lb. Suitable temperaturesinclude those from about 40 to 300 F. The higher temperatures, that is,from 150 to 300 F., are preferably employed when the feed stocks are invapor phase. At lower temperatures, for example, from 40 to 150 F.,isomerization can be effected in the liquid phase and without sidereactions. The time of the reaction varies with other factors such astemperature, the amount of catalyst, the particular catalyst used andthe particular feed stock treated. In general, however, the time ofreaction can be from /2 to 30 hours and the conditions are usuallyadjusted so as to paraflin converted to ample, between 100 and 150 F.The surprising feature of the novel process of this invention was thediscovery that at radiation dosages of between about 10- and 10 kWh f Paflin an isomerized. product can be obtained with a selcctivitysubstantially equal to 100 percent.

The amount of a eqjnum' chloride catalyst to be used varies widely,dependin cm the particular hydrocarbon which is to be converted,Preferably an amount in the range of from 2% to 200%by weightofhydrocarbon material present in the reactor imemployed.

The reaction is preferably carried out under liquid phase conditions,hence any temperat re below the critical temperature of the feed stockmay employed, although it is preferable to use the temperatu s specifiedabove. Suliicient super-atmospheric pressu be employed to maintain thereactant as well as the eaction products in the liquid phase under thereaction conditions obtained. In particular, liquid phase operations areconducive to the production of ultimate high yields and to the carryingout of the process in a continuous manner. The aluminum chloride can beadded to the feed before it enters the reactor. It is to be understood,however, that the process is not only applicable to continuousoperations, but it is contemplated to carry the same out in batch-typeapparatus for single batch operation. Where the reaction is carried outin the liquid phase, it is advantageous to intensively agitate thereaction mixture so that intimate contact is established between thefeed and the catalyst. In the present where a bed-type of catalyst isemployed, it is well to employ liquid phase operation and to force theliquid hydrocarbon feed into the reactor under pressure.

The invention can also be practiced by employing a "continuousbatch-type of operation" in which the reaction is carried out in liquidphase and the liquid product is removed after each batch reaction anddistilled or passed through a molecular sieve adsorption zone toseparate the isomerized product. Unconverted paraflins can then bereturned to the reaction zone in a subsequent charge. Preferably arecycle type of operation is employed.

The isomerization catalyst can be produced in situ by the reaction of asuitable metal such as aluminum with chlorine or a compound chemicallyreacting as the equivalent of free chlorine under the conditions of thereaction or may be added to the feed stock as chemically pure anhydrousaluminum chloride or as a commercial obtain a conversion of from 30%195% basedon feed product, at a temperature of, for excreased yields ofthe desired isomers. In another modi.-.

fication, a catalyst bed can be made up of Porocel or some othersuitable highly porous alumina and placed within the radiation zone. Thecatalyst mass employed can be formed by admixing granules of aluminumchloride with the desired quantities of dehydrated Porocel and the massheated while passing through a stream of inert vapor. Preferablyaluminum chloride, which 18 but sparingly soluble in hydrocarbons, isemployed as the isomerization catalyst for the process of the presentinvention. Aluminum bromide particularly is less desirable since itleads to excessive cracking. This is believed to be attributable to therelatively high solubility of aluminum bromide in hydrocarbon mixtures.

No special type of apparatus is required for carrying out the novelisomerization process of this invention. The novel features which arebelieved to be characteristic of the invention, both as to itsorganization and method of operation will be understood more clearly andfully from the following description considered in connection with theaccompanying drawing.

Referring to the drawing in detail, it will be seen that aluminumchloride is mixed with the normal parafiinic bymixture is exposed tohigh drocarbon to be converted and admitted to the process by line 1. Inthis manner the catalyst is fed into the radiation reactor zone 3. Asuitable support can be employed within the radiation zone on which thealuminum chloride lays down. Advantageously this support comprises ahighly porous aluminaof the Porocel type. Additional amounts of aluminumchloride are added from time to time if necessary by line 1. Methylcyclopentane is added to the process by line 7.

The aluminum chlorideparaffin-methyl cyclopentane energy ionizingradiation in the radiation zone 3. A suitable source of radiationcomprises atomic waste products obtained from nuclear reactors oratomicpiles. This material can be suitably enclosed or concentrated as in anunderground storage area, and the hydrocar on mixture can be passedthrough or around the waste rial.

The radiation 20115,; advantageously comprise a cohalt-60 source;Electron scelerators ot the linear type and Van de Graff geneia't rs canalso be employed as a source of high energy electrons. \The electronsare directed through a thin reinforced window into thehydrocarbon-aluminum chloride-naphthene mixture.

The converted material is removed by line 4 and passed into a suitableproduct separation zone. This zone can comprise, for example, adistillation zone, a solvent extraction zone, an absorption zone, amolecular sieve, or a sieves have the property of separatingstraightchained from branch-chained hydrocarbon isomers, as'

well as from cyclic and aromatic compounds. These zeolites haveinnumerable pores of uniform size, and only molecules small enough toenter the pores can be absorbed. The pores may vary in diameter from 3or 4 A. to about 15 A. or more, but it is a property of these zeolitesor molecular sieves that any particular product has pores ofsubstantially uniform size. Zeolites may vary somewhat in compositionbut generally contain the elements, silicon, aluminum, and oxygenoccurring and synthetic and sometimes termed aswellasanalkali metal oran alkali earth metal. A large number of naturally occurring zeoliteshaving molecular sieve activity, that is the ability to adsorb astraight-chained hydrocarbon and exclude or reject the branched-chainedisomers and aromatics because of diiferences in molecular size, aredescribed in an article entitled, Molecular Sieve Action of Solids,appearing in Quarterly Reviews, volume III, pages 293-320, 1949,published by the Chemical Society, London. Molecular sieves suitable forthe present invention comprise sieves having pore openings in the rangeof from about 4 to A. The molecular sieve heretofore described isarranged in any desired manner in the adsorption zone of separation zone5. It can, for example, be arranged on trays or packed therein with orwithout support. Conditions maintained in the molecular sieve treatmentin adsorption zone 5 are flow rates of about 0.1 to about 5 v./v./hr.,temperatures of about 200 to about 350 F. and pressures from atmosphericpressure to several p.s.i.g. With molecular sieves of the indicated sizeof pores, the normal paraffins contained in the feed are readilyabsorbed while the isoparaflinic product is not, but instead is passedby line 6 to suitable product containers. Unconverted normal parafiinicconstituents are recovered readily by the utilization of molecularsieves and returned by recycle process to the reactor by line 2 asindicated.

In order to more fully disclose the invention, the following example isgiven to indicate the nature of the invention. However, it should bedistinctly understood that this example is presented as merelyillustrative of a specific type of operation of the invention.

EXAMPLE 1 In this illustration methyl cyclopentane was added to the feedin the aluminum chloride catalyzed isomerization of normal hexane in thepresence of gamma radiation. In a typical experiment feed solutioncomposed of 92% by weight normal hexane and 8% methyl cyclopentane wasirradiated by cobalt-60 gammas of an intensity greater than l0kwh./lb./hr. in the presence of anhydrous aluminum chloride. The weightratio of aluminum chloride to feed was 1.5. The products obtained forthe same reaction with and without added methyl cyclopentane and withand without high energy ionizing radiation are given in Table I.

Table I With Added Without Added Methyl Methyl Cyclo- Cyolopenpentanetane Reaction Conditions:

Dose (mr.) 0 7. 2 0 10 71. 2 Temperature F.) 116 115 115 115 115Pressure (atm.) 1 1 1 1 1 Reactants (gins):

e.v 131 75 75 Product Yield (Wt. percent on Feed):

as 0 0 15. 8 23. 3 27. 8 n-hexane. 85.1 78. 4 38. 6 7. 2 3. 7 Co isomers14.9 21. 6 23. 6 26. 5 26. 4 2,2-dimethyl butane 0.3 0. 8 7. 5 13. 9 13.2 2-1nethyl pentane cyclopentane 2. 9 7. 8 12. 2 9. 3 9. 9 2,3-dimethylbutane 3-methyl pentane 1. 2 2. 3 3. 9 3. 3 3. 3 methyl cyclopentane.5.1 1. 9 0 O 0 cyclohexane 5. 4 8.8 0 0 0 Other liquid products 2 0 022.0 43. 0 42. 1

1 Analysis by vapor-liquid partition chromatography does not distinguishbetween these compounds.

2 C4, O5, O7 and O8 isomers.

The above example clearly shows that the addition of a cyclo paraflin tothe feed in the gamma radiolysis of aluminum chloride-hexane mixtureschanges the selec tivity of the reaction and avoids cracking of thefeed. It is seen that the reaction products in the case of the treatedfeed, that is, with added methyl cyclopentane, are

C isomers only, whereas products from cracking and alkylation alsoappear in the case of isomerization in the absence of a crackingsuppressor. In addition to increasing the radiation yield, methylcyclopentane also changes the distribution of products obtained in thenormal hexane-aluminum chloride reaction. These results show that methylcyclopentane can be used to suppress side reactions in radiationisomerization of saturates. In addition, radiation effectiveness isgreater when these side reactions are inhibited. The total G value interms of feed molecules reacted per E.V. was 131 as compared with a Gvalue of 75 obtained from untreated feed.

It is to be understood that the above-described arrange ments andtechniques are but illustrative of the applicaof the principles of theinvention. Numerous other arrangements and procedures may be devised bythose skilled in the art without departing from the spirit and scope ofthe invention.

What is claimed is:

1. A radiation isomerization process which comprises contacting ahydrocarbon mixture comprising a paraflin hydrocarbon having in therange of 4 to 8 carbon atoms and in the range of 2 to 20 wt. percent ofa naphthene having from 5 to 8 carbon atoms, with in the range of 2 to200 wt. percent of aluminum chloride based on the weight of parafiinhydrocarbon, and exposing said aluminum chloride in contact with saidhydrocarbon mixture at a temperature in the range of about 40 to 300 F.to. high energy ionizing radiation until a total dosage in the range of10- to 10 kwh. of radiation energy per pound of paraflin has beenabsorbed.

2.. A radiation isomerization process which comprises contacting aparaflinic hydrocarbon having from about 4 to 8 carbon atoms withaluminum chloride in the amount of about 2 to 200 wt. percent based onthe weight of paratlin, adding a naphthene having from 6 to 7 carbonatoms present in an amount of about 2 to- 20 wt. percent based upon theweight of paraffin, and exposing said aluminum chloride in contact withthe parafiinic hydrocarbon and said naphthene at a temperature in therange of about 40 to 300 F. to high energy ionizing radiation until atotal dosage in the range of 10- to 10 kwh. of radiation energy perpound of parafiin has been absorbed.

3. A radiation isomerization process which comprises contacting ahydrocarbon mixture consisting of from about 80 to 98 wt. percent ofnormal hexane and from about 2 to 20 wt. percent of methyl cyclopentanewith wt. percent based on the weight of hexane, of aluminum chloride,and exposing said aluminum chloride in contact with said mixture at atemperature in the range of about 40 to 150 F. at a pressure sufiicientto maintain liquid phase conditions, to from about 10- to 10megaroentgens of gamma radiation.

4. A hydrocarbon conversion process which comprises contacting ahydrocarbon feed comprising essentially paraflins having from about 4 to8 carbon atoms, with aluminum chloride present in the amount of about 2to 200 wt. percent and from about 2 to 20 wt. percent of a naphthenehaving from 6 to 7 carbon atoms, both based on the weight of paraffin inthe feed, and exposing the aluminum chloride in contact with said feedand said naphthene at a temperature of from about 40 to 300 F. to highenergy ionizing radiation until a total dosage in the range of 10 to 10kwh. of radiation energy per pound of paraffin has been absorbed.

5. A hydrocarbon conversion process which comprises contacting ahydrocarbon feed comprising essentially paraflins selected from thegroup consisting of n-butane, n-pentane, n-hexane, n-heptane, n-octaneand mixtures thereof, with (1) about 2 to 20 Wt. percent of a naphthenehaving from 6 to 7 carbon atoms and (2) about 2 to 200 wt. percent ofaluminum chloride, both based on the weight of parafiin in the feed, ata temperature of about 40 to 300 F., in the presence of a total dosageof high energy ionizing radiation in the range of 10- to 10 kwh.

7 per pound of paratfin sufiicient to convert between about 30 and 95wt. percent of said paraflins to reaction products.

6. A process for converting parafiin hydrocarbons which comprisescontacting a hydrocarbon feed comprising essentially paraflins havingfrom about 4 to 8 carbon atoms per molecule with (1) a naphthene havingfrom 6 to 7 carbon atoms present in an amount of about 2 to 20 wt.percent based on the weight of paraifin and (2) aluminum chloridepresent in the amount of about 2 to 200 wt. percent based on the weightof parafiin, exposing the aluminum chloride in contact with said feedand said naphthene at a temperature of from about 40 to 300 F. to atotal dosage of high energy ionizing radiation in the range of to 10kwh. per pound of hydrocarbon feed per hour, and recovering a convertedproduct in which the concentration of isomerized paraffin issubstantially equal to 100 percent.

7. A hydrocarbon conversion process which comprises contacting ahydrocarbon feed containing from about 2 to parts of methyl cyclopentaneand from about 80 to 98 parts of a paratfin having from 4 to 8 carbonatoms per molecule with aluminum chloride present in the amount of about2 to 200 wt. percent based on the weight of paralfin in the feed, andexposing the aluminum chloride in contact with said feed at atemperature of from about 40 to 300 F. to high energy ionizing radiationuntil a total dosage in the range of 10- to 10 kwh. of radiation energyper pound of parafiin has been absorbed.

8. An isomerization process which comprises charging a reactor with aparaffinic hydrocarbon having from about 4 to 8 carbon atoms permolecule and an aluminum chloride catalyst, said catalyst being presentin the amount of about 2 to 200 wt. percent based on the weight of saidparalfinic hydrocarbon, adding a naphthene having in the range of 5 to 8carbon atoms, said naphthene being present in an amount of about 2 to 20wt. percent based on the weight of paraflin, exposing said catalyst incontact with. said hydrocarbon to high energy ionizing radiation until,a total dosage in the range of 10- to 10 kwh. per poundof parafiin hasbeen absorbed, continuously removing the reaction product from thereactor, continuously separating the unconverted hydrocarbon from thedesired isoparatfin product, recycling said unconverted hydrocarbon tosaid reactor, and continuously feeding a fresh supply of hydrocarbon andnaphthene to the reactor.

9. A continuous isomerization process which comprises passing ahydrocarbon feed stock containing at least wt. percent of straight-chainparaflins having from 4 to 8 carbon atoms per molecule in contact with(1) in the range of 2 to 20 wt. percent of a naphthene having from 6 to7 carbon atoms and (2) a slurry comprising in the range of 2 to 200 wt.percent of an aluminum chloride catalyst, through a reaction chamberwherein said catalyst in contact with said hydrocarbon feed and saidnaphthene is subjected to high energy ionizing radiation until a totaldosage in the range of 10'- to 10 kwh. per pound of paraffin has beenabsorbed and continuously separating and withdrawing a product which hasbeen isomerized with a selectivity substantially equal to percent.

10. A process according to claim 8 wherein said iso paraflin product isseparated by absorption on a molecular sieve.

Proceedings of International Conference on Peaceful Uses of AtomicEnergy, vol. 15 (1955), page 28.

1. A RADIATION ISOMERIZATION PROCESS WHICH COMPRISES CONTACTING A HYDROCARBON MIXTURE COMPRISING PARAFFIN HYDROCARBON HAVING IN THE RANGE OF 4 TO 8 CARBON ATOMS AND IN THE RANGE OF 2 TO 20 WT. PERCENT OF A NAPHTHENE HAVING FROM 5 TO 8 CARBON ATOMS, WITH THE RANGE OF 2 TO 200 WT. PERCENT OF ALUMINUM CHLORIDE BASED ON THE WEIGHT OF PARAFFIN HYDROCARBON, AND EXPOSING SAID ALUMINUM CHLORIDE IN CONTACT WITH SAID HYDROCARBON MIXTURE AT A TEMPERATURE IN THE RANGE OF ABOUT 40* TO 800* F. TO HIGH ENERGY IONIZING RADIATION UNTIL A TOTAL DOSAGE IN THE RANGE OF 10**-6 TO 10**3 KWH. OF RADIATION ENERGY PER POUND OF PARAFFIN HAS BEEN ABSORBED. 